1. Field
The embodiments discussed herein are directed to a system, method, and devices related to fixed and transportable structures utilizing solar and wind technologies for generation of electricity.
2. Description of the Related Art
The world's ever-expanding population needs more and more electrical energy in order to power our machines, produce and distribute our products, cook our food, heat our homes, access and store our information, organize our activities, heal our ailing, care for our aged, entertain and communicate with each other and to physically transport our people from one place to another. All of this requires energy . . . a constant demand for reliable energy 24 hours a day, every hour, minute and second of every day of the year and all over the planet! Modern society and livelihood cannot exist as we know it without electricity. FIG. 1 shows energy usage at night in the United States and Central America as seen from outer space. FIG. 2 shows European and Asian energy usage at night as seen from outer space.
According to the U.S. Dept. of Energy, America's 81 million buildings consume more energy than any other sector of the U.S. economy, including transportation and industry.
Currently this demand for energy is dependent in great part on extracting fossil fuels from deep under ground in the form of oil, gas and coal . . . all of which produce various levels of pollution to our air, water and environment having a negative effect upon the health of humans as well as crops, plants livestock and animals.
According to many scientists, this pollution is becoming a factor in the changing climate, global warming or cooling and in turn is having an effect upon our weather patterns and climate changes which, in turn is anticipated to have an effect upon our food supply of fish, livestock and edible plants. However, the need for increasing amounts of energy continues to grow as we add more and more people to the world's population, and add more electronic and electrical devices designed for our comfort, survival, communication, distribution and entertainment.
Yet the need for clean energy is paramount so that we humans do not alter future generations, and acquire unhealthful conditions as we continue to breath ever-increasing exhaust fumes, poison our oceans, plants, wildlife and hence our food sources.
Problems with the Basic Energy Sources: Oil, Gas, Coal
The basic problems regarding fossil based energy sources are: Underground reserves of fossil forms of energy is finite and dwindling, Not replaceable, Increasing in costs of exploration meaning more expensive end-product for the consumer, Not healthful to climates, humans, plants and animals, It may be a major cause of global climate change to the earth's atmosphere, Controlled by many third-world dictators, Too versatile to use for fuel and would be better used in the manufacturing of petrochemical-based products.
Problems with Alternate Sources of Energy
Many companies, using a number of technologies, are exploring various ways of producing additional electrical energy and eventually fossil fuel replacement such as solar power that is limited to the production of electricity only when the sun is available and the current designs require large areas of land for the solar panels.
Wind Generation: Requires specific areas of wind turbulence and large, expensive propeller-driven machines to generate power. Requires frequent and costly maintenance, large areas of land or expensive ocean type support structures.
Wind power, on the other hand, has been used since ancient times to move ships and most notably in Holland where the famous wind mills use the force of the wind to power the process of grinding grain. More recently, wind power has been used to generate electricity using large propeller-driven turbines and the technology is plagued with problems ranging from bug residue to bird collisions. FIG. 3 shows wind power turbines in a “wind farm.”
A Global Problem . . . a Global Market
Emerging countries are faced with an overwhelming global concern for raising fuel costs and the dwindling world supply of oil needed to generate clean sources of cheap electricity. Many countries are seeking many different alternative forms of energy generation. This is a problem for both emerging nations as well as those nations with well-established energy generation infrastructures.
Up to this point, fossil fuels such as gasoline, oil, coal and natural gas have powered most of the growth of the world's economies, equipment and living conditions.
Other forms of energy sources such as tides present corrosion and maintenance problems, geothermal requires specific areas for implementation, and biofuels compete with human food requirements.
A Solution
The two major natural energy sources that are in abundance and ecologically friendly are solar power and wind power where man-made systems capture and convert their energy to usable electricity.
Solar energy radiating towards earth provides enough daily energy generated from the sun's rays shining upon a photovoltaic solar panel to produce electricity. It is clean, limitless, quiet, dependable and while the sun generates enough energy to meet the world's energy needs many times over, the challenge is to capture that power for our use at a reasonable cost.
Solar activity is limited to the daytime hours while wind generated electricity is also a competitive source of energy and it too is clean, but must be located is areas of steady wind. The example embodiments combine the advantages of each source of power into either fixed station systems or transportable systems, for example, for quick deployment in military, disaster relief, rural power generation applications. When it is quickly set up, the example embodiments will generate electricity 24 hours per day, seven days per week (24/7).
The portable or fixed station systems can be applied to a number of different application-dependent locations such as: along highways, railroads, bridges, in, on or adjacent to buildings, etc. and if they generate excess electricity, it can be used directly or resold to others including the utility power grid.
FIG. 4 illustrates one configuration of the embodiment where the two forms of natural energy, Solar and Wind are the primary sources for generating electricity via three core technologies:
Solar Energy, limited operation to the daylight hours
Solar Heat (Thermal) also limited operation to the daylight hours and
Wind Pressure(s) which is able to operate 24 hours per day as long as there is sufficient wind to move the turbine blades and the wind turbine generation system.
In the example embodiments, we are primarily interested in the generation of electricity. However, it is recognized that certain applications can also include different configurations or embodiments for the use of solar energy with the addition of appropriate technology for solar heat generation. These solar configurations may also be combined with an integrated wind power electrical turbine generation system for additional and continuous electricity generation.
The scope of example embodiments integrate various forms of natural occurring energy, i.e., solar photovoltaic 2 and wind 1 and to integrate them into either a fixed structure(s), as shown in FIG. 4A operating along a highway or railway train tracks, for example, or in the transportable embodiment(s) 3 (as shown in FIG. 4B) where they can, for example, be quickly moved by C-130 cargo planes or helicopters into a battlefield support area(s), added to ships, etc. to supply additional energy to support the military's need for electrical power in their operations, information systems, etc. where they operate in a variety of terrain, i.e., desert, jungle, on or under the water of lakes, oceans, etc. It can also be used in a number of embodiments and application for commercial and civilian use as described herein.
Solar Power
The sunlight that reaches Earth's surface delivers 10,000 times more energy than we consume, and solar power technologies aim to harness this potential energy source from space. Solar electric power systems transform the energy in sunlight into electricity. Sunlight is an abundant resource. Every minute the sun bathes the Earth in as much energy as the world consumes in an entire year.
Solar cells employ special materials called semiconductors that create electricity when exposed to light. Solar electric systems are quiet and easy to use, and they require no fuel other than sunlight. Because they contain no moving parts, they are durable, reliable, and easy to maintain.
Solar Statistics
FIG. 5 shows ranges of solar temperature on the Earth.
130,000 TW (Terrawatts) of energy falls on Earth from Sun. That's 1.1 kW/[perpendicular square meter] on the Earth's surface, when sky is clear. (AM1.5 spectrum)
15 TW was the mean total world energy consumption during 2005.
10 kW/person is the mean power (total—electricity, transportation, heating) used in the developed world.
The creation of electrical power utilizing the earth's sun as the original source of energy to generate electricity, has been in its embryonic stages for a number of decades. Recently, the electrical generation technologies are ready for commercialization on a large scale.
Today's solar energy technology converts the sun's light to electricity and absorbs its heat for heating and cooling systems. Large solar plants absorb the sun's heat to power steam turbines that produce electricity.
Present Status of Solar Energy
In 2007, the U.S. solar energy industry saw a promising future. The U.S. is the current world leader in the manufacture of both next-generation thin film technologies and the poly silicon feed stock used in most photovoltaic (PV) applications. U.S. PV manufacturing grew by 74 percent in 2007 and U.S. PV installations grew by 45 percent—both among the fastest growth rates in the world. Globally, the U.S. is the fourth largest market for PV installations behind world leaders Germany, Japan and Spain.
Perhaps surprisingly the United Kingdom (UK) receives 65% of the amount of solar radiation that is received by the south of Spain. The radiation in the UK is made up of direct radiation on sunny days, which accounts for around 40%, and diffused radiation on cloudy days, accounting for 60% of the annual total.
Spring—40 to 50% of domestic hot water requirements
Summer—80 to 90% of domestic hot water requirements
Autumn—40 to 50% of domestic hot water requirements
Winter—20 to 30% of domestic hot water requirements
Solar Power
The sunlight that reaches Earth's surface delivers 10,000 times more energy than we consume, and solar power technologies aim to harness this force. Solar technologies use any light source, however sunlight is “free” and provides heat, electricity, and even cooling for homes, businesses, and industry by conducting electrons across a photovoltaic array like the tiny solar cell in your calculator.
Researchers have optimistically proposed that if they could cover just 0.1 percent of the Earth's surface with highly efficient solar cells they could in theory replace all other forms of energy. At universities around the world, efforts are under way to develop the kinds of advanced solar arrays using nanotechnology and other cutting-edge science that could perhaps accomplish this goal in the future.
Applications of Solar Energy
A combination of solar electric arrays and pool-heating solar collectors were used to provide power and heat to the Georgia Tech University Aquatic Center, site of the 1996 Olympic swimming competition.
Solar electricity has powered satellites since the dawn of the space program. It has run remote communications outposts high in the mountains and turned on the lights, kept medicines cold, and pumped water in rural areas for more than 30 years. Small solar cells are used to power wristwatches, calculators, and other electronic gadgets. More recently, solar electric systems have been used to provide supplemental power to homes and commercial buildings in cities.
Solar electric technology has important roles to play in both the developing and developed worlds. From the farmer irrigating his crops in rural Mexico to an innovative lighting system for an Olympic sports arena, solar electric solutions abound.
Consumers and builders are integrating solar electric modules into their homes and buildings. Innovative solar electric technologies can replace conventional roofing and facade materials in new buildings. Solar electric roofing shingles, for example, are being used in some new residences. In grid-connected applications, solar electricity supplies some of a consumer's energy needs; the local utility provides the rest.
Standalone solar electric systems power a variety of applications far from the reaches of the power grid. These applications include remote communications systems such as television and radio transmitters and receivers, telephone systems, and microwave repeaters. Standalone solar electric power is also used to prevent corrosion of metal pipes, tanks, bridges, and buildings.
Many remote residences worldwide use solar electricity as their source of power. For instance, more than 100,000 vacation homes in Scandinavia rely solely on solar electric technology to run lights and appliances.
Villages around the world are building solar electric systems to bring electricity to their homes and local industries, often for the first time. To make the maximum use of available resources, village power is typically produced by a hybrid power system that combines solar electricity with diesel backup generators and sometimes another renewable energy technology such wind power. Villages also use standalone solar electric systems for pumping water—an application shared by rural farmers and ranchers in the United States.
Description of Forms of Energy Generation
Solar Heat (Thermal)
Electricity is also produced using the energy in the form of heat received from the sun to heat a liquid, mostly water, which is converted into steam which turns a steam generator which then turns a electrical generator producing electricity and in a different embodiment the system is capable of producing usable heat for warming purposes.
Solar Energy
Solar energy produces electricity through the conversion of sunlight into electricity by photoelectric process. There are a number of different forms capable of generating electricity such as, but not limited to photoelectric: cells, modules consisting of a plurality of cells, array of a plurality of modules, thin-film using adhesives or as laminates, special photovoltaic paint and/or fabric(s). FIG. 6 shows solar power collection.
Wind Pressure(s).
Wind pressure(s) turns turbine blades that either directly drives the electrical generator or indirectly drives the electrical generator using a gearbox, for example, to increase or decrease operational speed and the generation of electricity.
In the example embodiments, the wind turbine can continue to generate electricity even when there is no wind as the stored energy in the batteries received from the solar panels can be used to drive the wind turbine generators until the system senses the wind has returned then the stored energy in the batteries is turned to an “OFF” position.
Emerging Solar Technologies: Overview
Solar Photovoltaic: Definition
Photovoltaic (“PV”) is the field of technology and research related to the application of solar cells in producing electricity for practical use. The energy generated this way is an example of solar energy (also called solar power).
A solar cell or photovoltaic cell is a device that converts sunlight directly into electricity by the photovoltaic effect. Sometimes the term “solar cell” is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the source, i.e., the sun or other forms of light energy, is unspecified.
Therefore, the terms “Solar Panel” and “Photovoltaic Panel” describe two different devices. These terms, however, are often used interchangeably. In this application the terms refer to “the conversion of light's energy into electricity” whereas “Solar Heat” or “Thermal” would refer to using a light source's radiant heat, such as the sun, and heating water for heat or for the steam generation of electricity.
The Solar Industry
Research and development by companies and research labs are continually discovering new techniques and materials that improve efficiencies and cut the cost of capturing solar energy. The industry seeks to commercialize the most promising technology in order to improve delivery of solar power generation for homes, business and government.
Examples of various photovoltaic technologies capable of generating electricity from the sun include making and applying different combinations of materials for thin-film PV applications, solar cooling/heating systems, incorporating PV technologies into building materials for roofing, glass or plastic for windows and even PV paints applied to surfaces.
Other technological areas being aggressively pursued are storage systems (thermal and electrical); solar hybrid lighting; improved PV manufacturing techniques; PV down in the nanotechnology scale; low-cost semiconductor alternatives to polysilicon; and improving solar energy capture and concentration for higher efficiency power systems.
The increasing efficiency of solar energy technologies means we are able to purchase and install photovoltaic panels, knowing we are likely to receive an efficient way of harnessing energy from the suns rays to turn into usable electricity.
The Two Forms of Solar Generation for Electricity.
FIG. 7A Illustrates the sun 701 that radiates 702 upon the photovoltaic cells, modules and array(s) 703 and 704 converting the sun's energy into usable electricity 705.
FIG. 7B Illustrates the sun 706 that radiates 707 upon the solar energy collector's 708 reflected heat 712 and 713 that heats up the incoming liquid (water) 709 as it travels up the intake pipe 710 across 711 the solar collector 708 and down the return 714 as steam 715 and 716 that turns a steam engine 717 which then turns an electrical generator 718 which then produces electricity 719.
Solar Electric (Photovoltaic)
Solar cells, also known as Photovoltaic (PV) cells, do the work of making electricity. photovoltaic devices generate electricity directly from sunlight via an electronic process that occurs naturally in certain types of material. Electrons in certain types of crystals are freed by solar energy and can be induced to travel through an electrical circuit, powering any type of electronic device or storage for later use.
PV devices can be used to power anything from small electronics, such as calculators and road signs up to homes and large commercial businesses. It is an object of the example embodiments to expand the concept of local power generation to supply greater electrical needs than what a single house would use.
Solar Electric Power Systems
Several types of solar electric technology are under development, but four—crystalline silicon (a form of refined beach sand), thin films, concentrators, and thermophotovoltaics—are illustrative of the range of technologies that are capable of generating electricity. Solar cells are connected to a variety of other components to make a solar electric power system functional.
The approach described here (which uses electromagnetic induction to generate an alternating current) is just one way of producing electricity. There are also photoelectric, electrochemical, electromechanical, and thermoelectric phenomena (just to name a few) which can be used to produce an electric charge or direct-current electricity. Batteries are based on chemical reactions. Photovoltaic cells use light waves of specific wavelengths to excite electrons to cross from one layer of a semiconductor to another. A thermocouple can generate a current if the temperature at each junction is different. Fuel cells use hydrogen.
Crystalline Silicon
Crystalline silicon solar cells are used in more than half of all solar electric devices. Like most semiconductor devices, they include a positive layer (on the bottom) and a negative layer (on the top) that create an electrical field inside the cell. When a photon of light strikes a semiconductor, it releases electrons. The free electrons flow through the solar cell's bottom layer to a connecting wire as direct current (DC) electricity.
Some solar cells are made from polycrystalline silicon, which consists of several small silicon crystals. Polycrystalline silicon solar cells are cheaper to produce but somewhat less efficient than single-crystal silicon.
A simple silicon solar cell can power a watch or calculator. However, it produces only a tiny amount of electricity. Connected together, solar cells form modules that can generate substantial amounts of power. Modules are the building blocks of solar electric systems, which can produce enough power for a house, a rural medical clinic, or an entire village. Large arrays of solar electric modules can power satellites or provide electricity for utilities.
Solar Electric Power System Components
In addition to modules, several components are needed to complete a solar electric power system.
Many such systems include batteries, battery chargers, a backup generator, and a controller so that people in solar-powered homes and buildings can turn on the lights at night or run televisions or appliances on cloudy days. Grid-connected systems don't require batteries or backup generators because they use the grid for backup power. Some remote system applications, such as those used to pump water, do not require a backup power source.
Solar electric power systems can incorporate inverters or power control units to transform the DC electricity produced by the solar cells into alternating current (AC) to run AC appliances or for re-sale to a utility grid. Complete systems usually include safety disconnects, fuses, and a grounding circuit as well.
Thin Films
Solar electric thin films are lighter, more resilient, and easier to manufacture than crystalline silicon modules. The best-developed thin-film technology uses amorphous silicon, in which the atoms are not arranged in any particular order as they would be in a crystal. An amorphous silicon film only one micron thick can absorb 90% of the usable solar energy falling on it. Other thin-film materials include cadmium telluride and copper indium diselenide. Substantial cost savings are possible with this technology because thin films require relatively little semiconductor materials.
Thin films are produced as large, complete modules, not as individual cells that must be mounted in frames and wired together. They are manufactured by applying extremely thin layers of semiconductor material to a low-cost backing such as glass or plastic. Electrical contacts, antireflective coatings, and protective layers are also applied directly to the backing material. Thin films conform to the shape of the backing, a feature that allows them to be used in such innovative products as flexible solar electric roofing shingles.
Solar Concentrators
Solar concentrators use optical lenses (similar to plastic magnifying glasses), mirrors or reflective surfaces to concentrate the sunlight that falls onto a solar cell. With a concentrator to magnify the light's intensity, the solar cell produces more electricity. Today, most solar cells in concentrators are made from crystalline silicon. However, materials such as gallium arsenide and gallium indium phosphide are more efficient than silicon in solar electric concentrators and will most likely see more use in the near future. These materials are now used in communications satellites and other space applications.
Concentrators produce more electricity using less of the expensive semiconductor material than other solar electric systems. A basic concentrator unit consists of a lens to focus the light, a solar cell assembly, a housing element, a secondary concentrator to reflect off-center light rays onto the cell, a mechanism to dissipate excess heat, and various contacts and adhesives. The basic unit can be combined into modules of varying sizes and shapes. Concentrators only work with direct sunlight and operate most effectively in sunny, dry climates. They must be used with tracking systems to keep them pointed toward the sun.
Thermophotovoltaics
Thermophotovoltaic (TPV) devices convert heat into electricity in much the same way that other PV devices convert light into electricity. The difference is that TPV technology uses semiconductors “tuned” to the longer-wavelength, invisible infrared radiation emitted by warm objects. This technology is cleaner, quieter, and simpler than conventional power generation using steam turbines and generators.
TPV converters are relatively maintenance-free because they contain no moving parts. In addition to using solar energy, they can convert heat from any high-temperature heat source, including combustion of a fuel such as natural gas or propane, into electricity. TPV converters produce virtually no carbon monoxide and few emissions. They may be used in the future in gas furnaces that generate their own electricity for self-ignition (during power outages) and in portable generators and battery chargers.
Advantages
Solar electric systems offer many advantages. Standalone systems can eliminate the need to build expensive new power lines to remote locations. For rural and remote applications, solar electricity can cost less than any other means of producing electricity. Solar electric systems can also connect to existing power lines to boost electricity output during times of high demand such as on hot, sunny days when air conditioners are on.
Solar electric systems are flexible. Solar electric modules can stand on the ground or be mounted on rooftops. They can also be built into glass skylights and walls. They can be made to look like roof shingles and can even come equipped with devices to turn their DC output into the same AC utilities deliver to wall sockets. These advances mean individual homeowners and businesses can relieve pressure on local utilities struggling to meet the increasing demand for electricity.
More than 30 American states offer grid-connected solar electric systems for feeding any excess power generated by solar electric system produces into the utility grid an arrangement called net metering.
Solar power systems also require minimal maintenance. They run quietly and efficiently without polluting. The example embodiments may be combined with other types of electric generators such as wind, hydro, or natural gas turbines. They can charge batteries to make solar electricity continuously available.
For utilities, large-scale solar electric power plants can help meet demand for new power generation, especially in distributed applications. A solar electric power plant is created from multiple arrays that are interconnected electronically. Solar electric plants are easier to site and are quicker to build than conventional power plants. They are also easy to expand incrementally—by adding more modules—as power demand increases.
Solar electric power systems are good for the environment. When solar electric technologies displace fossil fuels for pumping water, lighting homes, or running appliances, they reduce the greenhouse gases and pollutants emitted into the atmosphere. The use of solar electric systems is particularly important in developing nations because it can help avert the expected increases in emissions of greenhouse gases caused by the growing demand for electricity in those countries.
Solar electric technologies also benefit the U.S. economy by creating jobs in U.S. companies. Exporting solar electric technologies to developing nations expands U.S. markets while protecting the global environment.
Solar Photovoltaic Systems
These operate on the principle of the photoelectric phenomenon—direct conversion of light to electricity. The solar radiation incident upon a silicon-based semiconductor photovoltaic cell produces direct electric current.
Photovoltaic cells are integrated into so-called modules with a voltage of 6-12 V, the electrically interconnected modules form solar array systems with an output voltage of 230 V and more.
Based on the installed capacity a distinction is made between: (1) Household solar systems with a capacity of several W or kW supplying DC to households via a battery, used for lighting and small appliances; (2) Major roof solar systems with a capacity of several kW supplying electricity surpluses (AC) in addition to supply to households to the public network; (3) Solar power plants with a capacity of several MW supplying the whole production to the public network.
Solar Concentration Thermal Power Plants
These operate on the principle of concentrating the sun's rays using mirrors into a small area (focal point) where the produced high heat is used to generate steam and electricity.
Three basic types are used to concentrate solar radiation: (1) Linear parabolic mirrors—concentrate solar radiation into a tube placed in the reflector focal point. Oil flows through the tube getting hot up to 400° C. and the heat is used to generate steam for the turbine connected to the electric generator; (2) Plate parabolic mirrors—concentrate solar radiation into an absorber positioned in the plate focal point. A liquid (oil) gets hot here up to 650° C. and the heat is used to generate steam for a small steam turbine featuring an electric generator; (3) Thermal solar towers—mirrors are arranged into a circle around the tower, being always turned toward the Sun and concentrating sun's rays into a collector (boiler) placed on the tower. Temperatures here come to over 1000° C. The heat is fed through thermo-oil to the steam generator where steam is generated to drive the turbine connected to the electric generator.
Photovoltaic History
The Photovoltaic effect was observed as early as 1890 by Henri Becquerel, and was the subject of scientific inquiry through the early twentieth century. In 1954, Bell Labs, in the United States, introduced the first solar PV device that produced a useable amount of electricity, and by 1958, solar cells were being used in a variety of small-scale scientific and commercial applications.
The energy crisis of the 1970s saw the beginning of major interest in using solar cells to produce electricity in homes and businesses, but prohibitive prices (nearly 30 times higher than the then current price) made large-scale applications impractical.
Industry developments and research in the following years made PV devices more feasible and a cycle of increasing production and decreasing costs began which continues even today.
What are Solar Panels?
Solar based systems collect energy from the sun converting it in two basic methods. They can indirectly generate electricity by capturing the sun's heat that in turn drives a steam engine and an electrical generator or as photovoltaic cells they convert the sun's energy directly into electricity.
There are two main forms of solar cells in existence today, and these are; “solar electricity systems” and “solar thermal systems”. The two different technologies allow application-dependent systems to either generate electricity or to heat the circulating water we use for example in heating the water in a swimming pool.
Solar panels that are designed to heat water work almost the same way as the sun heats the air. In a simple example, there is a pipe that runs through the inside of the box. The sun rays heat the air inside the box. The heat in the air is transferred to the pipes then the heat in the pipes is transferred to the water. As cool water is pumped into the inlet pipe the warm water is forced out of the outlet pipe. We can now use this warm water for something like a bath or shower.
These descriptions are only a simple representation of the basic concepts. In practice, solar water and air heaters can be more complex.
Solar Panels for Electricity Generation.
Using solar panels shown in FIG. 8 is a great way to generate clean and renewable electricity to power remote appliances, the average home or business and/or to supplement electricity to an existing electrical utility power grid.
As time goes by, we anticipate that emerging technologies will provide new and more efficient solar panel designs, systems and manufacturing methods. This is making the use of photovoltaic power over fossil fuels, much more viable to electric power companies, commercial applications, homeowners, light manufacturing and office environments.
Solar power collected by an electric company and/or its energy providers who have excess energy, will sell it into the electric company's power grid as a supplement source of energy and the electric company will resell it to their customers. This approach can save the electric companies the need to expand into other costly technologies for the generation of energy.
It is unlikely we will see heavy industry directly using photovoltaic electricity for quite some time due to the much larger energy demand industry requires.
As the technologies surrounding the use of photovoltaic improve, we are likely to see a much greater, widespread use of applications incorporating solar panels and related technologies.
Solar (or photovoltaic) cells, are a very useful way of providing electricity to remote areas (as mentioned earlier), where the use of electricity may be important, yet the laying of high voltage cable may not be viable. The best example of the importance of solar energy to provide electricity in remote locations can be found on satellites. For many years, satellites have been using solar panels to catch the suns rays, in order to provide power to the equipment on board.
Photovoltaic cells can be aligned as an array, as shown in FIG. 8. There are many advantages of using a solar cell array, with various panels fitted along a mounting system. One of the main advantages is that we are able to combine various numbers of cells to provide a greater output of electricity, and this method makes solar electricity a viable option to generate electrical power.
To optimize output from the panels, they should be installed in a south facing sloping roof at an angle between 30° to 45°. If a true south face is not available, a maximum deviation of 15° east or west from a true south orientation is recommended.
The panels can be fitted to a flat area, i.e., a roof with the use of a prefabricated frame capable of providing the panels with the correct angle. In all cases it is preferable to have the angle between 30° and 45°.
FIG. 9 illustrates the basic solar/photovoltaic process.
Solar Panel Construction
Assemblies of PV cells are used to make solar modules and a number of solar/PV modules make up solar photovoltaic arrays.
FIG. 10 illustrates a typical solar photovoltaic panel's array 1001 and construction 1002 where the photovoltaic cells 1004 are protected with a transparent protective material 1003 and a heat absorbing protective backing 1005.
Thin Film Photovoltaic Cells
Third generation technologies shown in FIG. 11 aim to enhance poor electrical performance of second generation (thin-film technologies) while maintaining very low production costs.
Current research is targeting conversion efficiencies of 30-60% while retaining low cost materials and manufacturing techniques. They can exceed the theoretical solar conversion efficiency limit for a single energy threshold material that was calculated in 1961 by Shockley and Queisser as 31% under 1 sun illumination and 40.8% under maximal concentration of sunlight (46,200 suns, which makes the latter limit more difficult to approach than the former).
There are a few approaches to achieving these high efficiencies: (1) Multi junction photovoltaic cell (multiple energy threshold devices); (2) Modifying incident spectrum (concentration); (3) Use of excess thermal generation (caused by UV light) to enhance voltages or carrier collection; (4) Use of infrared spectrum to produce electricity at night.
Thin film technologies include various approaches to converting sunlight into electricity, such as the use of: silicon nano structures; Up/Down converters; Hot-carrier cells; Thermoelectric cells, etc.
High efficiency solar cells are a class of solar cells that can generate electricity at higher efficiencies than conventional solar cells. While high efficiency solar cells are more efficient in terms of electrical output per incident energy (watt/watt), much of the industry is focused on the most cost efficient technologies (cost-per-watt or $/watt). Still, many businesses and academics are focused on increasing the electrical efficiency of cells, and much development is focused on high efficiency solar cells.
Solar Collector Panels for Heat Generation
The use of solar panels to heat water is becoming increasingly popular around the world due to the energy and money saved associated with this method.
A good solar hot water panel system is able to provide an average household with around a third of its annual hot water supply. While this may not sound much, it can reduce energy costs by a considerable amount.
Solar Generation: Heat and Electricity
Solar heating harnesses the power of the sun to provide solar thermal energy for solar hot water, solar space heating, and solar steam generation. A solar heating system saves energy, reduces utility costs, and produces clean energy. FIG. 12 illustrates a basic flow diagram of a solar heat system capable of generating electricity through the use of a steam turbine generator.
The efficiency and reliability of solar heating systems have increased dramatically, making them attractive options in the home or business. But there is still room for improvement. The U.S. Department of Energy (DOE) and its partners are working to design even more cost-effective solar heating systems and to improve the durability of materials used in those systems. This research is helping make these systems more accessible to the average consumer and helping individuals reduce their utility bills and the nation reduce its consumption of fossil fuels.
Wind Power Electricity Generation
Overview
The generation of electrical power utilizing the earth's sun as the original source of energy to generate electricity has been in its embryonic stages for a number of decades. Wind power on the other hand has been used since ancient times to move ships and most notably, the famous wind mills of Holland, where wind was used to power the process of grinding grain.
The wind turbine generator in FIG. 13 converts mechanical energy to electrical energy.
Wind turbine generators are a bit unusual, compared to other generating units ordinarily found attached to the electrical grid. One reason is that the generator has to work with a power source (the wind turbine rotor) which supplies very fluctuating mechanical power (torque).
Wind turbines may be designed with either synchronous or asynchronous generators, and with various forms of direct or indirect grid connection of the generator. Direct grid connection means that the generator is connected directly to the (usually 3-phase) alternating current grid.
Indirect grid connection means that the current from the turbine passes through a series of electric devices which adjust the current to match that of the grid. With an asynchronous generator this occurs automatically.
Generating Electricity at a Wind Power Plant
Wind power plants convert the air flow energy into electricity. The wind power drives the properly adjusted blades of the turbine rotor and makes them turn. The turning force of the rotor is transmitted via a gear or directly to the electric generator, where direct or alternating current is produced. The installed capacity of the largest wind turbines achieves 5,000 kW.
Wind power plants are divided by the magnitude of installed capacity into: (1) Micro sources—with capacities up to 30 kW—generate direct current for charging batteries; (2) Medium-sized power plants—with capacities up to 100 kW—supply alternating current to the network; and (3) Large power plants—with capacities over 100 kW—supply alternating current to the network.
According to the rotor axis position, there are two basic types of wind turbines: (1) With horizontal axis—all major installations; (2) With vertical axis—certain types of minor installations.
Turbines having a horizontal axis may also feature a rotor having one or two blades, but the majority has three blades.
A special group consists of wind power plants installed in coastal waters 10 to 20 miles off the coast. A larger number of wind turbines in a single location make up the so-called wind park or wind farm.
Starting (and Stopping) a Turbine
Most electronic wind turbine controllers are programmed to let the turbine run idle without grid connection at low wind speeds. (If it were grid connected at low wind speeds, it would in fact run as a motor, as you can read about on the generator page). Once the wind becomes powerful enough to turn the rotor and generator at their rated speed, it is important that the turbine generator becomes connected to the electrical grid at the right moment.
Otherwise there will be only the mechanical resistance in the gearbox and generator to prevent the rotor from accelerating, and eventually over speeding. (There are several safety devices, including fail-safe brakes, in case the correct start procedure fails.)
Soft Starting with Thyristors
If you switched a large wind turbine on to the grid with a normal switch, the neighbors would see a brownout (because of the current required to magnetize the generator) followed by a power peak due to the generator current surging into the grid. You may see the situation in the drawing in the accompanying browser window, where you see the flickering of the lamp when you operate the switch to start the wind turbine. The same effect can possibly be seen when you switch on your computer, and the transformer in its power supply all of a sudden becomes magnetized.
Another unpleasant side effect of using a “hard” switch would be to put a lot of extra wear on the gearbox, since the cut-in of the generator would work as if you all of a sudden slammed on the mechanical brake of the turbine.
Preventing “Islanding”
Islanding is a situation which may occur if a section of the electrical grid becomes disconnected from the main electrical grid, e.g. because of accidental or intended tripping of a large circuit breaker in the grid (e.g. due to lightning strikes or short circuits in the grid). If wind turbines keep on running in the isolated part of the grid, then it is very likely that the two separate grids will not be in phase after a short while.
Once the connection to the main grid is reestablished it may cause huge current surges in the grid and the wind turbine generator. It would also cause a large release of energy in the mechanical drive train (i.e. the shafts, the gear box and the rotor of the wind turbine) much like “hard switching” the turbine generator onto the grid would do.
The electronic controller of the wind turbine will therefore constantly have to monitor the voltage and frequency of the alternating current in the grid. In case the voltage or frequency of the local grid drift outside certain limits within a fraction of a second, the turbine will automatically disconnect from the grid, and stop itself immediately afterwards. This is normally done by activating the aerodynamic brakes.
Starting (and Stopping) a Turbine
Most electronic wind turbine controllers are programmed to let the turbine run idle without grid connection at low wind speeds. (If it were grid connected at low wind speeds, it would in fact run as a motor.) Once the wind becomes powerful enough to turn the rotor and generator at their rated speed, it is important that the turbine generator becomes connected to the electrical grid at the right moment.
Otherwise there will be only the mechanical resistance in the gearbox and generator to prevent the rotor from accelerating, and eventually “overspeeding”. (There are several safety devices, including fail-safe brakes, in case the correct start procedure fails).
Types of Turbine
There are various configurations and designs for wind generation turbine. Vertical spires, wind mill, spherical and horizontal designs all serve to produce the same result, to push a generator so that it will create electricity.
Wind Generation Problems
More recently, wind power has been used to generate electricity using large propeller-driven turbines as shown in FIG. 13. There are many problems with these propeller-driven turbines such as noise, high initial cost, the turbines must be placed in specific windy areas, aesthetics, size and the turbines require costly maintenance and a thick concrete base to support the heavy weight of the high tower and its torque when operating that these devices generate. The turbine's near-invisible propellers are a hazard to flying birds.
Another problem occurs on wind farms when insects fly into the propellers actually adding a gummy thickness to the props and reducing the air flow. This gummy mess requires a washing system to spray a cleaner onto the blades on a regular periodic basis in order to remove the insect buildup.